1. Field of the Invention
The present invention relates to a torque transmitting apparatus for transmitting torque from a driving source such as an engine to a rotary device such as an alternator or a compressor disposed within an engine room of a vehicle.
2. Description of Related Art
A rotary device such as a compressor which operates with power provided from an engine undergoes a change in torque fed thereto upon a change in load on the engine. When the torque fed to the rotary device changes, moving components oscillate, with consequent likelihood of noise generation.
The problem may be solved by adopting means such that a torque transfer member formed of an elastic material, that is, rubber, is disposed in a power transfer path extending from a drive source such as an engine up to a rotary device such as a compressor.
In this case, for absorbing a torque variation sufficiently it is desirable that the elastic modulus of the torque transfer member be set small. However, if the elastic modulus is set small, it becomes difficult to transfer a large torque and it is very likely to exceed an elastic limit of the torque transfer member. Thus, the durability of the torque transfer member may be worsened.
In the rotary device such as a compressor or a pump for power steering, required torque required on the rotary device side changes greatly, so that torque acting on a torque transmitting member differs greatly between the case where a torque variation is absorbed in a state in which the required torque is large and the case where a torque variation is absorbed in a state in which the required torque is small.
Therefore, by such a simple way as merely disposing in a power transmission path a torque transmitting member made of an elastic material such as rubber, it is difficult to absorb a torque fluctuation sufficiently in both cases of the required torque being large and small.
An object of the present invention is to allow a transmission of large torque while absorbing a torque fluctuation to a satisfactory extent.
According to a first aspect of the present invention, a torque transmitting member is deformed mainly by a flexural deformation when the amount of deformation is less than a predetermined amount and is deformed mainly by a compressive deformation when the amount of deformation is more than the predetermined amount. An elastic modulus of the torque transmitting member at a time when an amount of deformation is larger than the predetermined amount becomes larger than that at a time when an amount of deformation is less than the predetermined amount.
Thus, when the transmission torque fed from the driving source to the rotary device is small, the elastic modulus of the torque transmitting member becomes small, so that a fluctuation of the transmitting torque can be absorbed to a satisfactory extent. On the other hand, when the transmitting torque is large, the elastic modulus of the torque transmitting member becomes large, so that the torque transmitting member can be prevented from exceeding its elastic limit.
Thus, not only the transmission of a large torque can be done while absorbing a torque fluctuation sufficiently but also the torque transmitting member can be prevented from exceeding its elastic limit, thereby improving the durability of the torque transfer member.
Here, the elastic modulus of the torque transmitting member represents a change rate, K (=xcex94T/xcex94xcex8), of a transmission torque T transmitted between the first rotor and the second rotor relative to a relative rotational angle xcex8 of the first rotor with respect to the second rotor.
According to a second aspect of the present invention, an elastically deformable elastic member is disposed between a first curved surface of first rotor and a second curved surface of second rotor, and the elastic member is compressed by first and second curved surfaces to transmit a torque from the first rotor to the second rotor. A radius of curvature and a center of curvature of the first curved surface and a radius of curvature and a center of curvature of the second curved surface are made different from each other. Therefore, a change rate of the distance between the first and second curved surfaces at a time when a relative rotational angle of the first rotor with respect to the second rotor exceeds a predetermined amount is larger than a change rate of the distance between the first and second curved surfaces at a time when the relative rotational angle exceeds the predetermined amount.
Thus, when the torque is imposed on the first rotor and the first rotor rotates relatively with respect to the second rotor, as the relative rotational angle (xcex8) increases, the amount of movement of the first curved surface toward the second curved surface increases.
Consequently, the change rate of the distance between the first and second curved surfaces at a time when the relative rotational angle exceeds the predetermined amount becomes larger than that at a time when the relative rotational angle is less than the predetermined amount. In this case, since the elastic member is disposed between the first and second curved surfaces, as the relative rotational angle increases, the amount of compressive deformation of the elastic member in a non-linear fashion increases. That is, the transmission torque transmitted from the first rotor to the second rotor increases in a non-linear manner as the relative rotational angle becomes larger.
Therefore, even if an elastic material having a relatively large elastic modulus is selected as the elastic member, it is possible to decrease the amount of deflection at a relative rotational angle less than the predetermined amount, so that an elastic material having a relatively large elastic modulus can be used for the elastic member.
Further, since it is possible to prevent the elastic member from exceeding its elastic limit when the transmission torque becomes large, it is possible to transmit a large torque while absorbing a torque variation sufficiently.
According to a third aspect of the present invention, an outer periphery of the second rotor is generally star-shaped so as to have a plurality of projections, with a smooth curved surface being formed between adjacent projections, pins each having a circumferential surface with a radius smaller than a radius of curvature of the curved surface are provided in the first rotor so as to be each positioned between adjacent projections. An elastically deformable elastic member is disposed on the curved surface.
Thus, as the relative rotational angle of the first rotor with respect to the second rotor increases, the amount of compressive deformation of the elastic member increases in a non-linear manner. That is, as the relative rotational angle increases, the transmission torque increases in a non-linear manner.
Thus, even if an elastic material having a relatively large elastic modulus is adopted for the elastic member, it is possible to decrease the amount of deflection at a relative rotational angle less than a predetermined value, so that an elastic material having a relatively large elastic modulus can be used for the elastic member.
Further, since it is possible to prevent the elastic member from exceeding its elastic limit when the transfer torque becomes large, it is possible to effect the transfer of a large torque while absorbing a torque variation sufficiently.
According to a fourth aspect of the present invention, a torque transmitting member is deformable elastically and includes first and second transmitting members accommodated within the same space and having respective portions generally parallel to a compressive load direction which are different in size. When a relative rotational angle of the first rotor with respect to the second rotor is less than a predetermined rotational angle, the its first transmitting member mainly transmits the torque by undergoing a compressive deformation. On the other hand, when the relative rotational angle exceeds the predetermined rotational angle, the first and second transfer members share each other in bearing a compressive load to transmit the torque.
Thus, the relation between the relative rotational angle and the torque transmitted from the first rotor to the second rotor has a non-linear characteristic such that the torque becomes large with the arrival of the relative rotational angle at the predetermined relative rotational angle as a turning point.
The compressive deformation rate as referred to herein means a change rate of the transfer torque with respect to the relative rotational angle. As the compressive deformation rate increases, the transmission torque T with respect to the relative rotational angle becomes large.
Thus, even if a large torque is imposed on the torque transmitting apparatus, it is possible to prevent the torque transmitting member from exceeding its elastic limit, so that a torque fluctuation can be absorbed sufficiently under the transmission of a large torque.
According to a fifth aspect of the present invention, a torque transmitting member is formed so that a change rate of the transmission torque with respect to a relative rotational angle of the first rotor at a time when the first rotor rotates by a first predetermined angle or more in a forward direction relative to the second rotor is larger than the change rate at a time when if the first rotor rotates by a second predetermined angle or less, which is smaller than the first predetermined angle, in a reverse direction relative to the second rotor.
Thus, even if the required torque of the rotary device is large, it is possible to transmit a large torque and absorb a torque fluctuation sufficiently while preventing the torque transmitting member from exceeding its elastic limit.
On the other hand, when the required torque is small, a torque fluctuation can be absorbed even if the change rate is small. Thus, even when the required torque is small, it is possible to absorb a torque fluctuation to a satisfactory extent.
As mentioned above, it is possible to transfer a large torque while absorbing a torque fluctuation to a satisfactory extent.
According to a sixth aspect of the present invention, first and second torque transmitting members are accommodated respectively within plural spaces formed in the circumferential direction within the first and second rotors. The first and second torque transmitting members are elastically deformable and undergo a compressive deformation to transmit the torque. Before compressive deformation of the second torque transmitting member, an inner wall of a space where the second torque transmitting member is accommodated, out of the plural spaces, is spaced by a predetermined gap from the second torque transmitting member in a compressive load direction. When the first torque transmitting member is compressively deformed by a predetermined amount or more, the predetermined distance vanishes and a compressive load is imposed on the second torque transmitting member.
Thus, when the torque is exerted on the first rotor and the first rotor rotates relatively with respect to the second rotor, only the first torque transmitting member is deformed compressively until the relative rotational angle reaches a predetermined relative rotational angle.
When the first torque transmitting member is compressively deformed by the predetermined amount or more and the relative rotational angle reaches the predetermined relative rotational angle, a compressive load is exerted also on the second torque transmitting member, so that both the first and second torque transmitting members are deformed compressively.
Thus, the relation between the relative rotational angle and the torque transmitted from the first rotor to the second rotor has a non-linear characteristic such that as the relative rotational angle increases, the compressive deformation rate of the torque transmitting member increases.
The compressive deformation rate as referred to herein means a change rate of the transmission torque with respect to the relative rotational angle.
Thus, even if a large torque is imposed on the torque transmitting apparatus, it is possible to prevent the torque transmitting member from exceeding its elastic limit, so that a torque fluctuation can be absorbed sufficiently under the transmission of a large torque.
According to a seventh aspect of the present invention, a torque transmitting member is deformable elastically and undergoes a compressive deformation to transmit the torque. When a relative rotational angle of the first rotor with respect to the second rotor is smaller than a predetermined rotational angle, the torque transmitting member undergoes a compressive deformation so that the cross-sectional area in a cross-section nearly perpendicular to the direction of a compressive load imposed on the torque transmitting member increases. When the relative rotational angle is smaller than the predetermined rotational angle, the torque transmitting member undergoes a compressive deformation while inhibiting an increase of the cross-sectional area.
In the case where the compressive deformation takes place so as to bring about an increase of the cross-sectional area, the freedom of the deformation is large in comparison with the case where the compressive deformation takes place in an increase-inhibited state of the cross-sectional area. A change rate (elastic modulus k) of the compressive load with respect to a relative rotational angle of the first rotor relative to the second rotor in case of the compressive deformation being done so as to result in an increase of the cross-sectional area is smaller than the elastic modulus k in case of the compressive deformation being done in an increase-inhibited state of the cross-sectional area.
Thus, the elastic modulus k) of the torque transmitting member at a large relative rotational angle is larger than that at a small relative rotational angle.
Thus, even if a large torque is imposed on the torque transmitting apparatus, it is possible to prevent the torque transmitting member from exceeding its elastic limit and hence possible to absorb a torque fluctuation sufficiently under the transmission of a large torque.
According to an eighth aspect of the present invention, a torque transmitting member accommodated within a space formed within the first and second rotors. The torque transmitting member is deformable elastically and undergoes a compressive deformation to transmit the torque. When a compressive load is not imposed on the torque transmitting member, a gap is formed between a portion of an inner wall of the space which is nearly parallel to the direction of the compressive load and the torque transmitting member.
Thus, when the relative rotational angle is small, the torque transmitting member is deformed compressively so as to increase the cross-sectional area thereof and thereby fill up the gap. After the gap has vanished, the torque transmitting member is compressively deformed in an increase-inhibited state of the cross-sectional area. Therefore, the elastic modulus k of the torque transmitting member is large when the relative rotational angle is large in comparison with the case where the relative rotational angle is small.
Thus, even if a large torque is exerted on the torque transmitting apparatus, it is possible to prevent the torque transmitting member from exceeding its elastic limit and hence possible to absorb a torque fluctuation sufficiently under the transmission of a large torque.
According to a ninth aspect of the present invention, a torque transmitting member accommodated within a space formed within first and second rotors, the torque transmitting member is deformable elastically and undergoes a compressive deformation to transmit the torque. An end portion of the torque transmitting member in a direction nearly parallel to the direction of a compressive load acting on the torque transmitting member is tapered so as to be smaller in cross-sectional area toward a front end side thereof. Therefore, when a compressive load is not imposed on the torque transmitting member, a gap is formed between an inner wall of the space and the torque transmitting member.
Thus, the torque transmitting member is deformed compressively so that the gap becomes smaller as the relative rotational angle increases from the state of it being zero. Thus, the torque transmitting member has a non-linear characteristic such that as the relative rotational angle increases, the elastic modulus k increases.
Therefore, even if a large torque acts on the torque transmitting apparatus, it is possible to prevent the torque transmitting member from exceeding its elastic limit and hence possible to absorb a torque fluctuation sufficiently under the transmission of a large torque.
According to a tenth aspect of the present invention, the torque transmitting member is deformable elastically and undergoes a compressive deformation to transmit the torque. The torque transmitting member is deformed compressively so that at least when a relative rotational angle of the first rotor with respect to the second rotor is smaller than a predetermined rotational angle, as the relative rotational angle increases, the area of contact between a portion of an inner wall of the space which is nearly parallel to the direction of the compressive load and the torque transmitting member increases.
Thus, the torque transmitting member is deformed compressively in such a manner that the freedom of deformation becomes smaller as the relative rotational angle increases from the state of it being zero. As a result, the torque transmitting member comes to have a non-linear characteristic such that as the relative rotational angle increases, the elastic modulus k of the torque transmitting member increases.
Thus, even if a large torque acts on the torque transmitting apparatus, the torque transmitting member can be prevented from exceeding its elastic limit and so it is possible to absorb a torque fluctuation to a satisfactory extent under the transmission of a large torque.
According to an eleventh aspect of the present invention, a torque transmitting member is accommodated within a space formed within first and second rotors. The torque transmitting member is deformable elastically and undergoes a compressive deformation to transmit the torque. When a compressive load is not imposed on the torque transmitting member, a gap is formed between an inner wall of the space and the torque transmitting member.
Thus, the torque transmitting member is deformed compressively so that the gap becomes smaller as the relative rotational angle increases from the state of it being zero. As a result, the torque transmitting member comes to have a non-linear characteristic such that as the relative rotational angle increases, the elastic modulus k thereof increases.
Thus, even if a large torque acts on the torque transmitting apparatus, it is possible to prevent the torque transmitting member from exceeding its elastic limit and hence possible to absorb a torque fluctuation to a satisfactory extent under the transmission of a large torque.